Polymer bearings for cranes

In-Depth 12 Sep 2024 by Paul Avery

Energy chain specialist igus presented a new range of lubrication-free and corrosion-resistant polymer bearings for container cranes.

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Polymer bearings for cranes — Installation points for igus igutex polymer bearings on an RTG. The bearings can also be used on STS cranes © igus

Bearings and bushings in STS and yard crane boogie assemblies are typically made of steel. igus states that steel bearings at a container terminal, where conditions include dirt, dust, salty air, heat, cold and humidity, require regular lubrication and are subject to premature wear and failure.

By contrast new polymer bearings from the igutex series are made of high-performance plastic and are extremely robust and wear-resistant, as well as being corrosion-free and insensitive to dirt. Furthermore, they do not require any lubrication.

The product was presented at TOC Europe in Rotterdam in June.

Heavy duty

A bearing or bushing in a boogie on an STS crane weighing over 2,000t is a very demanding application. Igus says it is possible to use polymers in this application thanks to a new process called igutex.

“igus manufactures most lubrication-free plain bearings with plastic injection moulding. However, the material structure does not offer sufficient mechanical stability for heavy-duty applications such as chassis bearing support for cranes with surface pressures of more than 80MPa. The company therefore uses igutex to manufacture composite plain bearings in a two-stage winding process. To do this, the winding machine first produces an inner layer of filament fabric with integrated solid lubricants. The microscopically small lubricant particles are gradually released during movement and enable dry operation with low coefficients of friction. In the second winding, a protective outer shell is created from a resin-impregnated and particularly hard-wearing fibreglass fabric.”

“Thanks to this two-stage winding, the polymer bearings in the igutex series achieve a maximum permissible surface pressure of up to 200MPa,” added Uwe Sund, Product Manager for iglidur Heavy-Duty Bearings at igus. “The polymer bearings are robust enough to work in STS cranes with low wear and fail-safe operation.”

To demonstrate the durability of igutex, igus tested its wound polymer bearings against steel and bronze bearings in its own laboratory.

“Bearings with a diameter and length of 40mm each were loaded with 80MPa on a test rig. They swivelled 50,000 times by 50° – at a speed of 30 swivels per minute. The result: the steel bearing (15MnCr5) suffered such massive shaft wear that the engineers had to abort the test after 10,000 cycles. After the same time, the bronze bearing failed due to wear on the bearing itself,” igus said. “The polymer bearing from the igutex series, on the other hand, survived the 50,000 cycles with only minimal signs of wear.”

Costs lower than steel

The new polymer bearings are available for new cranes and as a retrofit for existing units. Igus can manufacture the bearings, which usually have a diameter of 100mm and higher, to identical measurements as required.

Speaking to WCN, Muhammed Gencol, igus Sales Manager / Key Account Manager Industry Cranes, said the initial cost of polymer bearings is generally lower than for steel. The cost of ownership is significantly lower, as lubrication of the bearings is eliminated completely.

Most specifications can be met with standard bearings from a catalogue, but igus can produce customised units if needed Igus keeps standard bearings in stock, while customised bearings have a lead time of 2-3 weeks.